Preparation method of nitrile rubber with high oil resistance

Abstract

The invention discloses a preparation method of high-oil-resistance nitrile rubber, which comprises the following components in parts by weight: 275 parts of soft water, 50-55 parts of butadiene and 45-50 parts of acrylonitrile, wherein the addition amount of butadiene and acrylonitrile is 100 parts; the emulsifier is a dodecylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt composite system, and the dosage of the emulsifier is 2.5-5 parts; the initiator adopts persulfate, and the use amount of the initiator is 0.1-0.5 part; 0.1 part of triethanolamine; the preparation method comprises the following steps: synthesizing butyronitrile rubber cement by adopting an intermittent feeding mode of replenishing a molecular weight regulator in batches and a thermal polymerization process, adding a terminating agent and an anti-aging agent, and degassing, condensing, washing and drying to obtain a high-strength butyronitrile rubber product. The nitrile rubber has the Mooney viscosity ML (1 + 4) 100 DEG C of 90-120, the tensile strength of more than or equal to 27.5 MPa and the elongation at break of more than or equal to 450%, and can meet the application requirements in the fields of automobiles, aerospace, sealing washers and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber preparation, and in particular relates to a method for preparing highly oil-resistant nitrile rubber. Background Art

[0002] Due to its excellent oil resistance, benzene resistance, heat resistance and physical and mechanical properties, nitrile rubber is widely used in the fields of automobiles, aerospace, sealing gaskets, etc. The above fields have more stringent requirements on the performance of rubber, and have higher requirements on the oil resistance, combined acrylonitrile, Mooney viscosity, etc. of rubber. In terms of polymerization process, Zeon Company of Japan adjusts the polymerization temperature appropriately, uses potassium persulfate as initiator, potassium oleate, sodium dodecylbenzene sulfonate and other negative ions or non-ionic surfactants such as polyoxyethylene alkyl ether as emulsifiers, and dodecyl mercaptan as a regulator to obtain NBR with ML (1+4) of 30-150 at 100°C, molecular weight distribution index of 5-8, gel content of less than 5%, and combined acrylonitrile content of 10%-45%, which is used in rubber products industries such as rubber rollers; in the prior art, the combined acrylonitrile content of nitrile rubber is mostly less than 40%, which cannot meet the use requirements of rubber in the fields of automobiles, aerospace, sealing gaskets, etc.; and the monomer conversion rate during the polymerization process is about 75%, which is not high enough. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing highly oil-resistant nitrile rubber, which solves the problem in the prior art that the combined acrylonitrile content is less than 40% and the conversion rate is not high enough. The present invention achieves the improvement of the polymerization conversion rate while ensuring that the rubber properties are not affected by accurately controlling the pH value of the polymerization system. On the basis of the prior art, a nitrile rubber with high oil resistance, higher combined acrylonitrile and better Mooney viscosity is prepared.

[0004] The technical scheme adopted by the present invention is a method for preparing a highly oil-resistant nitrile rubber, wherein butadiene and acrylonitrile are used as polymerization monomers, and the emulsification system is compositely used with sodium salts of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate. The pH value of the polymerization system is controlled by sodium (potassium) hydroxide, the initiation system adopts persulfates, such as water-soluble initiators such as potassium persulfate and ammonium persulfate, and the molecular weight regulator is tert-dodecyl mercaptan. The intermittent feeding method of adding the molecular weight regulator in batches is adopted to synthesize the nitrile rubber slurry, add a terminator and an antioxidant, and obtain a highly oil-resistant nitrile rubber after degassing, coagulation, washing and drying. The specific details are as follows:

[0005] The invention comprises 275 parts of soft water, 50-55 parts of butadiene and 45-50 parts of acrylonitrile based on 100 parts by weight of the added amount of butadiene and acrylonitrile; the emulsifier is a composite system of sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, and the amount of the emulsifier is 2.5-5 parts; the initiator is a persulfate, and the amount thereof is 0.1-0.5 parts; the triethanolamine is 0.1 parts; the molecular weight regulator is added in an amount of 0.3-0.7 parts in three times;

[0006] The above raw materials are mixed to cause polymerization reaction, and the pH value of the polymerization system is 10.0-11.0; when the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added; when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added, and when the reaction conversion rate reaches 85-90%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and high-strength special nitrile rubber is obtained after degassing, condensation, washing and drying.

[0007] The present invention is also characterized in that:

[0008] Preferably, the amount of dodecylbenzenesulfonic acid used is 2 to 4.5 parts, and the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt used is 0.5 to 1 part.

[0009] Preferably, the molecular weight regulator is tert-dodecyl mercaptan.

[0010] Preferably, the molecular weight regulator is added in three equal portions.

[0011] Preferably, the polymerization reaction temperature is controlled at 30-40°C.

[0012] Preferably, the initiator is potassium persulfate.

[0013] The polymerization conversion rate of the nitrile rubber of the invention reaches 85-90%, thereby improving the primary utilization rate of the monomer, reducing the energy consumption of monomer recovery, and increasing the production capacity of the polymerization equipment.

[0014] The beneficial effect of the present invention is that the present invention adopts the emulsification system of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt, controls the pH value of the polymerization system and uses the thermal intermittent emulsion polymerization process to synthesize highly oil-resistant nitrile rubber, which has an acrylonitrile content of 40-45% and a Mooney viscosity of ML (1+4) 100℃ 90~120, tensile strength≥27.5MPa, elongation at break≥450%. The nitrile rubber produced by the present invention meets the application requirements in the fields of automobiles, aerospace, sealing gaskets, etc. In addition, when the present invention is used to synthesize the mortar, the polymerization process is stable and the energy consumption is low. DETAILED DESCRIPTION

[0015] The present invention is described in detail below in conjunction with specific implementation modes.

[0016] The method for preparing highly oil-resistant nitrile rubber of the present invention adopts an emulsification system compounded with sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, controls the pH value of the polymerization system and uses a thermal intermittent emulsion polymerization process to prepare a method for preparing highly oil-resistant nitrile rubber, which is specifically as follows:

[0017] Butadiene and acrylonitrile are used as polymerization monomers, and the emulsification system uses sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate. The pH value of the polymerization system is controlled by sodium (potassium) hydroxide, and the initiation system uses persulfates, such as potassium persulfate, ammonium persulfate and other water-soluble initiators. The molecular weight regulator is tert-dodecyl mercaptan. The intermittent feeding method of adding the molecular weight regulator in batches is used to synthesize the nitrile rubber slurry, add a terminator and an antioxidant, and obtain a highly oil-resistant nitrile rubber after degassing, coagulation, washing and drying. Specifically:

[0018] The monomer composition is (based on 100 parts by weight of butadiene and acrylonitrile, the same below) 50-55 parts of butadiene, 45-50 parts of acrylonitrile, 275 parts of soft water, the emulsifier is a composite system of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt, the emulsifier is used in an amount of 2.5-5 parts, the dodecylbenzenesulfonic acid is used in an amount of 2-4.5 parts, and the naphthalenesulfonic acid formaldehyde condensate sodium salt is used in an amount of 0.5-1 part; the initiator is 0.1-0.5 parts; 0.1 part of triethanolamine; the pH value of the polymerization system is 10.0-11.0. The monomer and initiator are added once, the molecular weight regulator is added three times, and the intermittent emulsion polymerization is carried out, and the polymerization temperature is 30-40°C.

[0019] After the polymerization kettle is evacuated, soft water, emulsifier, part or all of the monomers and triethanolamine are added, and after the temperature is raised to 30-40° C., an initiator is added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added. When the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 85-90%, the temperature is lowered to 20-25° C., the material is discharged, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0020] The high oil-resistant nitrile rubber produced by the invention has an acrylonitrile content of 40-45%, and has high tensile strength and elongation at break, and can meet the application requirements in the fields of automobiles, aerospace, sealing gaskets, etc.

[0021] The test methods for rubber use conventional test methods: total solids test uses SH / T1154-92 standard; combined acrylonitrile test uses SH / T1157-1997 standard; Mooney viscosity MS (1+4)The 100℃ test adopts the GB / T1232.1-2000 standard; the tensile strength test adopts the GB / T528-1998 standard; the elongation at break test adopts the GB / T528-1998 standard.

[0022] Effect of the invention: The technology of the present invention can produce acrylonitrile content of 40-45% and Mooney viscosity ML (1 +4) 100℃ 90~120, tensile strength ≥27.5MPa, elongation at break ≥450%. The nitrile rubber produced by the present invention meets the application requirements in the fields of automobiles, aerospace, sealing gaskets, etc. In addition, when the mortar is synthesized by using the present invention, the polymerization process is stable and the energy consumption is low.

[0023] Example 1

[0024] The polymerization kettle is evacuated, replaced with nitrogen, and the vacuum degree reaches -0.1Mpa. 275 parts of soft water, 55 parts of butadiene, 45 parts of acrylonitrile, emulsifier (including 3 parts of dodecylbenzenesulfonic acid, 0.5 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.1 parts of triethanolamine, 0.15 parts of molecular weight regulator are added in sequence, and the pH value of the polymerization system is 10.3. Then the temperature is raised, and when the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added, and when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 88%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0025] Example 2

[0026] The polymerization kettle is evacuated, replaced with nitrogen, and the vacuum degree reaches -0.1Mpa. 275 parts of soft water, 52 parts of butadiene, 48 parts of acrylonitrile, emulsifier (including 2 parts of dodecylbenzenesulfonic acid, 0.5 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.1 parts of triethanolamine, 0.15 parts of molecular weight regulator are added in sequence, and the pH value of the polymerization system is 10.5. Then the temperature is raised, and when the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added, and when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 88%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0027] Example 3

[0028] The polymerization kettle is evacuated, replaced with nitrogen, and the vacuum degree reaches -0.1Mpa. 275 parts of soft water, 56 parts of butadiene, 44 parts of acrylonitrile, emulsifier (including 2.5 parts of dodecylbenzenesulfonic acid, 0.8 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.1 parts of triethanolamine, 0.15 parts of molecular weight regulator are added in sequence, and the pH value of the polymerization system is 10.5. Then the temperature is raised, and when the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added, and when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 86%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0029] Example 4

[0030] The polymerization kettle is evacuated, replaced with nitrogen, and the vacuum degree reaches -0.1Mpa. 275 parts of soft water, 57 parts of butadiene, 43 parts of acrylonitrile, emulsifier (including 3.5 parts of dodecylbenzenesulfonic acid, 0.8 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.1 parts of triethanolamine, 0.15 parts of molecular weight regulator are added in sequence, and the pH value of the polymerization system is 10.6. Then the temperature is raised, and when the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added, and when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 88%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0031] Example 5

[0032] The polymerization kettle is evacuated, replaced with nitrogen, and the vacuum degree reaches -0.1Mpa. 275 parts of soft water, 52 parts of butadiene, 48 parts of acrylonitrile, emulsifier (including 2.5 parts of dodecylbenzenesulfonic acid, 0.8 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.1 parts of triethanolamine, 0.15 parts of molecular weight regulator are added in sequence, and the pH value of the polymerization system is 10.8. Then the temperature is raised, and when the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added, and when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 90%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0033] Comparative Example 1

[0034] The 10L polymerization kettle is evacuated, replaced with nitrogen, and the vacuum degree reaches -0.1Mpa. 275 parts of soft water, 55 parts of butadiene, 45 parts of acrylonitrile, emulsifier (6 parts of dodecylbenzenesulfonic acid, 0.05 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.1 parts of triethanolamine, 0.5 parts of molecular weight regulator are added in sequence, and the pH value of the polymerization system is 10.3. Then the temperature is raised, and when the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added, and when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 92%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and a highly oil-resistant nitrile rubber is obtained after degassing, condensation, washing and drying.

[0035] Comparative Example 2

[0036] A 10L polymerization kettle is evacuated and replaced with nitrogen until the vacuum reaches -0.1Mpa. 275 parts of soft water, 52 parts of butadiene, 48 parts of acrylonitrile, 0.5 parts of sodium salt of naphthalenesulfonic acid formaldehyde condensate, 0.1 parts of triethanolamine, and 0.5 parts of molecular weight regulator are added in sequence. The pH value of the polymerization system is 9.5. Then the temperature is raised. When the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added. When the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 92%, the material is discharged after cooling to 20-25°C. A terminator and an antioxidant are added. After degassing, condensation, washing and drying, a highly oil-resistant nitrile rubber is obtained.

[0037] Comparative Example 3

[0038] A 10L polymerization kettle is evacuated and replaced with nitrogen until the vacuum reaches -0.1Mpa. 275 parts of soft water, 52 parts of butadiene, 48 parts of acrylonitrile, 0.1 parts of sodium salt of naphthalenesulfonic acid formaldehyde condensate, 0.1 parts of triethanolamine, and 0.5 parts of molecular weight regulator are added in sequence. The pH value of the polymerization system is 9.5. Then the temperature is raised. When the reaction temperature reaches 30°C, 0.2 parts of initiator potassium persulfate are added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added. When the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 70%, the material is discharged after cooling to 20-25°C. A terminator and an antioxidant are added. After degassing, condensation, washing and drying, a highly oil-resistant nitrile rubber is obtained.

[0039] The nitrile rubber produced by the present invention has high tensile strength and elongation at break, and can meet the application requirements in the fields of automobiles, aerospace, sealing gaskets, etc.

[0040] As shown in Table 1, the high oil-resistant special nitrile rubber prepared in Examples 1-5 and the experimental conditions in Comparative Examples 1-3 are compared. The test results of the performance of the nitrile rubber are shown in Table 2 below: As can be seen from Table 2, the nitrile rubber is synthesized by using a composite emulsification system of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt and a thermal emulsion polymerization process. The Mooney viscosity ML (1 +4) 100℃ 90~120, tensile strength ≥27.5MPa, elongation at break ≥450%.

[0041] Table 1

[0042]

[0043]

[0044] Table 2

[0045]

[0046] In the present invention, as the polymerization conversion rate of the nitrile rubber emulsion polymerization increases, the rubber-bound acrylonitrile content increases and the Mooney viscosity increases, but as the conversion rate increases, the rubber performance deteriorates. The present invention achieves the improvement of the polymerization conversion rate while ensuring that the rubber performance is not affected by the precise control of the pH value of the polymerization system.

Claims

1. A method for preparing highly oil-resistant nitrile rubber, characterized in that: The details are as follows: The invention comprises 275 parts of soft water, 50-55 parts of butadiene and 45-50 parts of acrylonitrile based on 100 parts by weight of the added amount of butadiene and acrylonitrile; the emulsifier is a composite system of sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, and the amount of the emulsifier is 2.5-5 parts; the initiator is a persulfate, and the amount thereof is 0.1-0.5 parts; the triethanolamine is 0.1 parts; the molecular weight regulator is added in an amount of 0.3-0.7 parts in three times; The above raw materials are mixed to cause polymerization reaction, and the pH value of the polymerization system is 10.0-11.0; when the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added; when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added, and when the reaction conversion rate reaches 85-90%, the material is discharged after cooling to 20-25°C, a terminator and an antioxidant are added, and high-strength special nitrile rubber is obtained after degassing, condensation, washing and drying.

2. The method for preparing the highly oil-resistant nitrile rubber according to claim 1, characterized in that: The dosage of the dodecylbenzenesulfonic acid is 2 to 4.5 parts, and the dosage of the naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.5 to 1 part.

3. The method for preparing the highly oil-resistant nitrile rubber according to claim 2, characterized in that: The molecular weight regulator is tert-dodecyl mercaptan.

4. The method for preparing the highly oil-resistant nitrile rubber according to claim 1, characterized in that: The molecular weight regulator was added in three equal portions.

5. The method for preparing the highly oil-resistant nitrile rubber according to claim 1, characterized in that: The polymerization reaction temperature is controlled at 30-40°C.

6. The method for preparing the highly oil-resistant nitrile rubber according to claim 1, characterized in that: The initiator is potassium persulfate.

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